This invention relates to an improved computed tomography (CT) system. More specifically, this invention relates to an improved CT detector module.
In at least one known CT system, an X-ray source projects a fan-shaped beam which is collimated to lie within an X-y plane of a Cartesian coordinate system and generally referred to as the “imaging plane.” The X-ray beam passes through the object being imaged, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array is dependent upon the attenuation of the X-ray beam by the object. Each detector element of the array produces a separate electrical signal that is a measurement of the beam attenuation at the detector location. The attenuation measurements from all the detectors are acquired separately to produce a transmission profile.
In known third generation CT systems, the X-ray source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged so that the angle at which the X-ray beam intersects the object constantly changes. A group of X-ray attenuation measurements, i.e., projection data, from the detector array at one gantry angle is referred to as a “view.” A “scan” of the object comprises a set of views made at different gantry angles, or view angles, during one revolution the X-ray source and detector. In an axial scan, the projection data is processed to construct an image that corresponds to a two dimensional slice taken through the object. One method of reconstructing an image from a set of projection data is referred to in the art as the “filtered back” projection technique or process. This process converts the attenuation measurements from a scan into integers called “CT numbers” or “Hounsfield units” which are used to control the brightness of a corresponding pixel in a cathode ray tube display.
At least one known detector CT imaging system includes a plurality of detector modules each having a plurality of detector cells having a scintillator array optically coupled to a semiconductor photodiode array that detects light output by the scintillator array. These known detector module assemblies require an increasing number of scintillator/diode rows in the Z direction, along with associated electronics to support a desire for increasing the number of CT slices of information gathered per CT rotation.
Therefore, it would be desirable to provide a method for using existing CT detector modules that sum detector cells in the Z-direction. It would be further desirable to provide a method for staggering the summed detector cells. It is also desirable to provide such a method wherein the method of the present invention is implemented using Field Effect Transistor (FET) switch arrays.